1. Field of the Invention
The present invention relates to a heating unit constituted by arranging radiant heaters, and relates to a resin sheet heating apparatus using the heating unit.
Priority is claimed on Japanese Patent Application No. 2006-232255, filed Aug. 29, 2006, the content of which is incorporated herein by reference.
2. Description of Related Art
Conventionally, as the type of heating unit described above, a heating unit has been proposed, as disclosed, for example, in Japanese Patent No. 3576080 and Japanese Unexamined Patent Application, First Publication No. 2003-181912, in which radiant heaters are arranged in a grid configuration on a frame, each radian heater including a support plate having a substantially square plate shape and a strip-shaped heater element provided on the support plate.
In this heater unit, the strip-shaped beater element is directly heated by supplying electrical power to the strip-shaped heater element, and a heated object is heated using radiant heat from the strip-shaped heater element, and thus a resin sheet, for example, can be evenly heated by the radiant heaters that are arranged in a grid configuration.
In such a heating unit, the temperature of the strip-shaped heater element can be adjusted by changing electrical current or voltage being supplied to the strip-shaped heater element, and the state of heating of the heated object due to the radiant heater can be controlled in a preferable responsive manner.
Incidentally, in the conventional heating unit, because the radiant heaters are individually mounted one after another on the frame of the heater unit, the mounting work and connecting work for wirings to be connected to the radiant heaters are complicated and require long time and much workload.
Moreover, when the radiant heater thermally deforms during a heating operation, the support plates of the radiant heaters adjacent to each other may interfere each other, and the heated object may not be evenly heated. To prevent this problem, it is necessary to adjust the gap between the radiant heaters; however, it is a further complicated difficult work to mount many radiant heaters on the frame while taking the gap between the radiant heaters into account.